Cisco Certified Network Associate: Day 3 (PM) - Subnetting

Instructor: Imran Rafai

Overview

• Focus on subnetting, primarily for Class C IP addresses.
• Class B and Class A, along with Supernetting, will be covered in a future session (Day 3 Late Night).

Subnetting Basics

• Subnetting: Breaking down a large network into smaller, manageable networks.
• Analogy: Like dividing a large room into two with a wall.

IP Address Types

• Private IP Addresses:
  • Class A: 10.0.0.0 to 10.255.255.255 (16,777,216 addresses)
  • Class B: 172.16.0.0 to 172.31.255.255 (1,048,576 addresses)
  • Class C: 192.168.0.0 to 192.168.255.255 (65,536 addresses)
• Public IP Addresses:
  • Assigned to routers facing the internet. Local devices get private IPs.

Historical Context

• IPv4's Limitation: Originally designed with 4.2 billion addresses, initially thought to be sufficient.
• IPv6 & NAT: Developed due to rapid internet growth and IPv4 exhaustion.
• Subnetting Need: Emerged to efficiently utilize available IPs as demand increased.

Class C IP Address Subnetting

• Example Used: 192.168.100.225 / Subnet Mask: 255.255.255.0 (Slash 24)
• Network & Host Identification:
  • Network ID: All host bits 0
  • Range: From 192.168.100.1 to 192.168.100.254
  • Broadcast ID: All host bits 1 (192.168.100.255)

Transition to Classless

• CIDR Notation: Shift to Classless Inter-Domain Routing (CIDR) with subnetting
• Slash Notation: Represents number of bits in network portion (e.g., /24)

Breaking Down Networks

• Borrowing bits from host part creates subnets:
  • Example 1: Borrow 1 bit > Two subnets with /25
  • Example 2: Borrow 2 bits > Four subnets with /26

Subnetting Exercise

• Convert subnet mask to binary and determine block size & network IDs.
• Magic Table: Useful for determining subnets and block size.

Variable Length Subnet Mask (VLSM)

• VLSM: Allows different subnet sizes to match specific needs.
• Example: Design networks for departments with varying host requirements.

Practical Application

• Practice problems involving network ID and broadcast ID identification.
• Emphasis on speed and accuracy for CCNA exams.

Final Notes

• Practice: Essential for mastering subnetting.
• Resource Utilization: Video material and comments for questions and clarifications.
• Preparation: Necessary for CCNA certification and real-world applications.

End of Day 3 (PM) Session. Upcoming: Class A and B Subnetting & Supernetting.

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